1. Field of the Invention
The present invention relates generally to fastening devices adapted for securing structural members together, such as metal plates, panels of wood, plastic sheets and the like; and more particularly to drive rivets which are adapted for retaining such structural members together by driving a pin or the like through a shaped opening formed in the rivet in order for expanding a number of pronged members thereon which fasten the members together.
2. Brief Description of the Prior Art
Drive rivets have been known in the art for many years for use in fastening a plurality of various separate structural members, panels or the like together as a unit. Generally, such rivets are first installed within preformed holes which are drilled or punched through each respective structural member. A preformed head is usually included which abuts against the first member when installed and on the distal end are a number of pronged members which protrude outwardly through the hole that is formed in the last member. A drive pin or the like is then driven through an opening formed within the center of the head of the rivet which works to expand the prongs outwardly and against the underside of the last member in order for securing the members together against the underside of the preformed head.
Generally, the force which is required for driving or installing a drive pin within a drive rivet is dependent upon the total thickness of the members which are to be fastened. For example, with increased thicknesses, the force which is required for installing the pin can be very high, and, as such, it is oftentimes difficult or impossible, in such applications, to drive the pin within the rivet and thereby expand the prongs. Specifically, there is a particular range of thicknesses with which a rivet can operate satisfactorily; with the maximum thickness being of value which will allow pin installation into the rivet with a level of force reasonable to the user.
As such, there is a need for an improved drive rivet having a greater range of operation; in particular one which is capable of being used with increased thicknesses, and which will not require a significant increase in the level of force necessary for installation of the drive pin.
The drive rivet of the present invention is adapted for retaining in a fastened position at least a first and a second panel member of varying aggregate thicknesses. The first and second panel members each include an inner and an outer surface, and also an aperture therethrough for receiving the drive rivet for installation. The drive rivet includes a head portion formed on one end which abuts the outer surface of the first panel member when installed. A generally elongated shank portion is also included which extends inwardly from the head portion and through the apertures of the first and second panel members. The shank portion is included with an outer shank surface which includes at least a first and a second area. The first area of the outer shank surface is of a substantially constant diameter. The second area of the outer shank surface is of a diameter less than that of the first area and is not in engagement with the panel members when installed. The drive rivet also includes at least a first generally elongated bore extending from the head portion and into the shank. In addition, a plurality of expansible prongs are formed on the distal end of the shank which extend at least through the second area in the shank""s outer surface. An expander pin is included which is driven into the bore of the drive rivet in order to expand the prongs outwardly for retaining the first and second panels in the fastened position. During the time when the expander pin is being driven into the bore, the second area of the shank""s outer surface moves to engage at least the second panel member as the prongs are being expanded outwardly.
Advantageously, the present invention provides an improved drive rivet which is capable of fastening a plurality of panel members having an increased total thickness.
Furthermore, it is another advantage of the present invention to provide a drive rivet capable of fastening a plurality of panel members having an increased total thickness without also requiring a significant increase in the level of force necessary for installation of the rivet drive pin.